The Stillwater River is an 11.5 miles (18.5 km) side channel of the Penobscot River

Penobscot River

The Penobscot River is a river in the U.S. state of Maine. Including the river's West Branch and South Branch increases the Penobscot's length to , making it the second longest river system in Maine and the longest entirely in the state. Its drainage basin contains .It arises from four branches...

 in Maine

Maine

Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...

. From its source (44.9664°N 68.6458 °W) in Old Town

Old Town, Maine

Old Town is a city in Penobscot County, Maine, United States. The population was 7,840 at the 2010 census. The city's developed area is chiefly located on a relatively large island, though its boundaries extend beyond that...

, the Stillwater runs 2.3 miles (3.7 km) northwest along the northeast side of Orson Island, the site of the Penobscot Indian Reservation. It then runs 9.2 miles (14.8 km) south along the west sides of Orson and Marsh islands, over three dammed falls. The stream rejoins the main stem of the Penobscot in Orono

Orono, Maine

Orono is a town in Penobscot County, Maine, United States. It was first settled in 1774 and named in honor of Chief Joseph Orono of the Penobscot Nation. It is home to The University of Maine. The population was 10,362 at the 2010 census.- Geography :...

.